Combine objects from an array with the same date into new array of objects using Javascript

Question

I have an array of objects that looks like this:

var data = [
{Date: "01-01-2000", Banana: 10},
{Date: "01-01-2000", Apple: 15},
{Date: "01-01-2000", Orange: 20},
{Date: "01-02-2000", Banana: 25},
{Date: "01-02-2000", Apple: 30},
{Date: "01-02-2000", Orange: 35}];

And I would like to know how to merge the objects in this array by the same date values so that the following array is returned:

data = [
{Date: "01-01-2000", Banana: 10, Apple: 15, Orange: 20},
{Date: "01-02-2000", Banana: 25, Apple: 30, Orange: 35}];

My apologies if this is a duplicate question, I just have not been able to find an example where the key & value pairs are different in each object and so I thought I would at least ask.

Possible duplicate of Sum javascript object propertyA values with same object propertyB in array of objects — lumio
– lumio, Commented Oct 19, 2018 at 19:51
Possible duplicate of Combine json arrays by key, javascript — phadaphunk
– phadaphunk, Commented Oct 19, 2018 at 19:52

Ele · Accepted Answer · 2018-10-19 19:55:21Z

1

An alternative is using the function reduce to group the objects along with the function Object.values to extract the grouped objects.

var data = [{Date: "01-01-2000", Banana: 10},{Date: "01-01-2000", Apple: 15},{Date: "01-01-2000", Orange: 20},{Date: "01-02-2000", Banana: 25},{Date: "01-02-2000", Apple: 30},{Date: "01-02-2000", Orange: 35}],
    result = Object.values(data.reduce((a, c) => {
      a[c.Date] = Object.assign(a[c.Date] || {}, c);
      return a;
    }, {}));

console.log(result);

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answered Oct 19, 2018 at 19:55

Ele

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1 Comment

Calvin Whitehurst Over a year ago

This is correct, thank you so much. I spent way too much time trying to figure this out on my own.

s.meijer · Accepted Answer · 2020-08-14 20:54:59Z

0

Alternatively, you can use a for loop.

Try:

var data = [{Date: "01-01-2000", Banana: 10},{Date: "01-01-2000", Apple: 15},{Date: "01-01-2000", Orange: 20},{Date: "01-02-2000", Banana: 25},{Date: "01-02-2000", Apple: 30},{Date: "01-02-2000", Orange: 35}];
var obj = {};
for(var i = 0; i < data.length; i++){
   var date = data[i].Date;
   // Get previous date saved inside the result
   var p_date = obj[date] || {}; 
   // Merge the previous date with the next date
   obj[date] = Object.assign(p_date, data[i]);
}

// Convert to an array
var result = Object.values(obj);

console.log(result);

edited Aug 14, 2020 at 20:54

s.meijer

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answered Oct 19, 2018 at 20:15

Mzndako

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